Self-insulated discharge tube terminal



Patented Nov. 22, 1932 FRED HOTCHNER, OF LOS ANGELES, CALIFORNIASELF-INSULATED DISCHARGE TUBE TERMINAL Application Med November 14,1930. Serial No. 495,648.

- This invention relates to self-insulated discharge tube terminals, theobject thereof being to provide a terminal for discharge tubes such as,for instance, luminous posltive column discharge tubes in the form ofinscriptions as used in electric signs, which terminal need have noinsulation other than that pro vided by its own construction at theplace where it passes through the sign body.

In general, this invention pertains to any type of discharge tube whichis to be insulated as against some outside element of the device inwhich it is installed, The insulation of discharge tubes for displayWork is an extremely diiicult matter and at the present time a greatsource of annoyance and expense, also imposing certain limitations uponthe construction of the apparatus, which are very undesirable.

It is to be borne in mind in the case of this illustration of theinvention that rather high voltages are used and high frequenciessometimes are present due to characteristics of the circuit. Coronadischarges tend to form and break down any insulation used at theterminal. In sign work, this is aggravated by the presence ofaccumulated dirt and moisture. A strict limitation is placed by theconditions .0f the Work upon the material which may be used forinsulation in the prior art, such materials as rubber being excluded,and materials of the character of porcelain and glass being required.

The problem of insulating terminals of discharge tubes for sign Work hasbeen and still is a source of great annoyance. It has been found that,considered the country over, weather conditions have caused thediscarding of practically all types of insulating terminals exceptingthe open housing type, that is, the end of the tube extends into theorcelain housing which extends backward into the body of the sign, thehousing being open to the weather and of such size that water will runout. This is an extreme construction from the early attempts atinsulation which by various devices closed the housing to the weather byrubber gaskets, porcelain caps, or the like. 5 The use of the presenttype of housing is tends which is frequently out of proportion veryobjectionable in the art as they are awkward to install and unsightlyand furthermore do not fully accomplish the purpose for which they areintended.

The necessity of providing a Wide opening in the housing makes itessential to observe a minimum dimension for the Width of the signletters through which the housing exto the size of the letters. Hence agreat many signs are made with the tubing formed to bend sideways andpass into the sign through housings installed through the main body benside the letters, an obvious makeshift and expensive construction, butone which nevertheless must be followed in a good percentage of cases ifthe tube is to be properly insulated.

The present invention eliminates the necessity for large housings andpermits the construction of signs with practically no limitation in thelay-out of the copy or construction of the letters so far as housingsare concerned. Due to the fact that the tendency to form coronadischarges is overcome at tlie point the terminal enters the body of thesign, rubber gaskets may be used in connection with this type ofterminal without fear of disintegration of the rubber by the discharge,thus providing for the construction of water-tight signs.

The objects of the invention therefore, are to provide a discharge tubeterminal which is provided with insulation Within the tube, which isproof against breakdown through the tube at the place the tube passesthrough a supporting body, which is free from corona action, and whichcan be installed in direct contact with the supporting body to effect aWater tight construction.

A further object of the invention is to reduce the cost of the terminalconstruction in the sign. Other objects Will be apparent from thefollowing speciication and claims.

The invention is not limited to devices of the particular typeillustrated but may be vvariously embodied in different types ofdischarge tubes and thus it is to be understood as being limited only bythe prior art and I l the limitations specifically imposed by the vas ashield.

Numeral 1 in Fig. 1 indicates a typical discharge tube terminal of thetype used herein as an illustration of the invention, 2 belng theportion which extends into the sign body making contact with theterminal sprlng 3 supported from an insulating post 4 wh1ch is fastenedto the inside 5 of the sign face 6. The electrode 7 is of an internaltype and is supported from the re-entrant stem 8, the lead-in conductor9 extending through the stem and ending in the metallic contact 10 whichcontacts with the spring 3. The insulation is here provided by aconducting shield 11, which extends within the tube between two limitsselected a material distance away Jfrom the plane of the sign face 6.Each end of this shield is provided with beads 1.2, 12, etc., as shownin the perspective view 1n Fig. 2, which spaces the shield a very littledistance away from the inside wall 13 of the tube. The beads may befused to the shield 11 in a manner well known in the art. The shield ispositioned lengthwise in the tube by the offset shoulders 50 and 51. Thespace 14. between the outside surface 15 of the shield and insidesurface 13 of the tube is made comparable to the length of the mean freepath of the atoms of the contained gas within the tube. By comparable ismeant slightly greater, the same, or less, in length, inasmuch as thephrase length of the mean free path is a somewhat uncertain quantity,the criteria here being that 'this dimension being reduced to a point atwhich a d1scharge cannot occur from the surface 15 of the shield 11through the wall of the tube to the sign face 6. As is well known in theIn the variation of the invention shown in Fig. 3, two shields are used,numbered 17 and 18, the shield 17 being provided with the beads 19, 19,etc. in the same manner as in the illustration above, the shield 1.8having flared portions 20 and 21 which also terminate in beads 22, 22,etc. There are beads placed at the ends 23 and 24 of the shield 17 tospace the same lengthwise with respect to the shield 18. In this view,the electrode is indicated by 25, the reentrance stem by 26, the lead-inwire by 27 and the terminal by 23. The object of this variation of theinvention is to provide additional insulation to that provided by thesingle annular space shown in Fig. 1, by the insulating e'tect of thespace 29 and also to take the potential oil' of the shield 17, therebyrelieving the space 30 from the duty of resisting the potential from theterminal to ground.

A further variation of the invention is shown `in Fig. 4, in which anelectrode 31 is shown made on the principle disclosed in several of mypreviously filed patent applications. such as Serial No. 302,473, whichhas resulted in Patent No. 1,789,901, and which provides for theconstruction of an electrode oextremely small dimensions capable ofcarrymg the load of very large electrodes of the prior art. In thisview, 32 is a wall of the tube and it will here be seen that this hasbeen greatly reduced in cross section as compared with the dischargetube proper 33, utilizing the characteristics of this particularelectrode and of the instant invention. The end 34 of the electrode ispositioned from the walls of the tube by the beads 35, 35, etc., as isshown above, or obviously by any other suitable method so as to providea space 36 of such small width that a discharge may not form between theoutside wall 37 and the inside wall 38 of the tube 32.

As a further variation I illustrate a rubber ring 39, which in thisinvention, may be used without danger, because even though the rubbermay deteriorate and become conduct-v ing, it cannot cause breakdown. Itwill also be seen that in the variation in Fig. 4, I have provided aconstruction far in advance of anything known in the prior art, ofextreme practicability and simplicity, and one which completely solvesthe need for an insulating positive column discharge tube for sign workas well as in numerous other instances inthe discharge tube art.

Having thus described a particular embodiment of my invention as anillustratio thereof, what I claim is:

1. The combination of a metallic supporting member for a discharge tube,a hole therethrough, through which extends a terminal of said dischargetube, the diameter of said hole as compared with the diameter of thel'tube being such that additional insulation is necessary other thanthat of the wall of the tube itself, a shield within said tube extendingboth ways from the plane of said supporting member, the distance betweenthe outside surface of said shield and the inside surface of said tubebeing so small that the insulating effect of a small space in thecontaining gaseous medium in such discharge tube provides the additionalinsulation needed.

2. In a discharge tube, a shield of conducting material within said tubeparallelly disposed to and spaced a distance from the inside wall ofsaid tube so small that the gaseous medium therebetween may not becomeconducting under normal operating conditions, and an additonalshield ofconducting material within said irst shield parallelly disposed to andspaced a distance therefrom so small that the gaseous mediumtherebetween may not become conducting under normal operatingconditions.

3. In an electric display` a metallic sign body, a discharge tubepositioned on said sign body, said discharge tube having a terminalextending into said body, said terminal being provided with aninsulating body of gas within said tube at the place where said tubeenters said sign body.

4. In an electric display, a metallic sign' body, a discharge tubepositioned on said sign body. said discharge tube having a terminalextending into said body, said terminal being provided with aninsulating body of gas within-said tube at the place where said tubeenters said sign body; the opening in said sign body through which saidterminals ex tends being slightly greater in diameter than the outsidediameter of said terminal, and a closure of yieldable material closingthe opening between said terminal and the material of said sign body.

5. In a gaseous conduction tube mounting wherein the tube is mountedupon a support and extends through a conductive portion thereof, meansfor preventing breakdown discharge from the interior of the tube to saidportion comprising shielding means within said tube, and extending onopposite sides of said portion.

6. In a gaseous conduction tube mounting wherein the tube is mountedupon a support and extends through a. conductive portion thereof, means'ier preventing breakdown discharge trom the interior of the tube tosaid portion comprising shielding means within said tube.

'2'. In gaseous conduction tube mounting wherein the tube is mountedupon a support and extends through a conductive portion thereof, meansfor preventing break down discharge from the interior of the tube tosaid portion comprising shielding means within said tube, including asleeve within said tube opposite said portion.

8. In a gaseous conduction tube mounting wherein the tube is mountedupon a support and extends through a conductive portion thereof, meansfor preventin breakdown discharge from the interior o? the tube to saidportion comprising shielding means within said tube, including a sleevewithin said tube opposite said portion and spaced from the Wall of saidtube.

9. In a gaseous conduction tube mounting wherein the tube is mountedupon a support and extends through a conductive portion thereof, meansfor preventing breakdown discharge from the interior of the tube to saidportion, comprising means substantially preventing ionization of the gasimmediately adjacent the wall of said tube for a substantial distancealong the tube on both sides of said portion.

10. In a gaseous conduction tube mounting wherein the tube is mountedupon a support and extends through a conductive portion thereof, meansfor preventing breakdown from the interior of the tube to said portionconsisting of an internal electrode positioned opposite said portion andextending a distance on each side thereof, the outer surface of saidelectrode being positioned so close to the inner wall of said tube thatthe gaseous medium remaining in the space therebetween is incapable ofconducting by virtue of the insulating eifect of very thin layers ofgas.

l1. In a gaseous conduction tube mounting wherein the tube is mountedupon a support and extends through a conductive portion thereof, meansfor preventing breakdown from the interior of said tube to said portionconsisting of an internal electrode positioned opposite said portion andextending a distance on each side thereof, the outside diameter of saidelectrode being slightly less than the inside diameter of said tube atsaid portion, and means to position said electrode in said tube so thata very small space remains therebetween ot such small thickness that thegaseous medium therein is nonconducting.

Signed at llos Angeles, California, this 10th day of November, 1930.

FRED HGTCHNER.

